Problem

Dorico 3.5 hangs on launch. In the start screen, the following message is being displayed indefinitely: 

"Audio engine: Waiting for connection" 

Background

This problem can occur if you have installed an incompatible HALion Sonic SE version, for example by trying out Dorico 4 on an unsupported macOS version. 

Solution

If this is the case, "downdating" the existing HALion Sonic SE installation to HALion Sonic SE 3.4.40 will solve the issue.

• Restart your computer to make sure no Dorico process is still running. 
• Download and run this HALion Sonic SE uninstaller. 
• Download and reinstall HALion Sonic SE 3.4.40. 

Now it should be possible to start Dorico 3.5 again.